In a liquid crystal display apparatus for displaying a color image, a color is displayed by an additive color mixture of three primary colors. Therefore, in a transmissive liquid crystal display apparatus, a backlight device capable of irradiating a liquid crystal panel with white light including a red component, a green component, and a blue component is required. In the related art, a cold cathode fluorescent tube called a CCFL has been widely adopted as a light source of the backlight device. However, in recent years, adoption of an LED is increasing from viewpoints of lower power consumption and easiness of luminance control. For example, the backlight device having a configuration using a red LED, a green LED, and the blue LED as a light source has been known in the related art.
In recent years, as a technique for realizing widening of color gamut, a technique of obtaining white light by combining the blue LED and a phosphor sheet is gaining attention. The phosphor sheet adopted in the technique functions as a wavelength conversion sheet that converts a wavelength of light emitted from the blue LED so as to obtain white light. In order to realize this, the phosphor sheet contains a phosphor (fluorochrome) that is excited by the light emitted from the blue LED and emits light. Specific examples of the phosphor sheet to be used include a phosphor sheet including a yellow phosphor, or a phosphor sheet including a green phosphor and a red phosphor. There is known a backlight device having a configuration using a white LED (white LED package) with a configuration in which the blue LED is covered with the yellow phosphor as a light source.
FIG. 25 is a side view showing a schematic configuration of a backlight device that obtains white light by a combination of a blue LED and a phosphor sheet (wavelength conversion sheet) in the related art. The backlight device includes a plurality of blue LEDs 93 as a light source, an LED substrate 92 on which the plurality of blue LEDs 93 are mounted, a diffuser plate 94 that diffuses light emitted from the blue LEDs 93 and flatly uniformizes the light, a phosphor sheet 95 that converts a wavelength of the light emitted from the blue LEDs 93 so as to obtain white light, an optical sheet 96 that improves light utilization efficiency, and a chassis that supports the LED substrate 92 and the like. Note that, the chassis is not illustrated in FIG. 25. In the configuration using the blue LED 93 as a light source, the phosphor sheet (for example, phosphor sheet including yellow phosphor) 95 is provided as shown in FIG. 25, so that white light is emitted from the backlight device as backlight light.
In relation to the present disclosure, for example, in Japanese Unexamined Patent Application Publication No. 2015-32373 discloses an disclosure of a light source apparatus that obtains white light by a combination of blue light source and a wavelength conversion sheet. In the light source apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2015-32373, a diffusing member for uniformizing angular distribution of incident light is disposed between the blue light source and the wavelength conversion sheet in order to improve the quality of the illumination light.